A variety of semiconductor chip packages are known that provide support for a semiconductor die, such as an integrated circuit (IC) die, and associated bond wires, provide protection from the environment, and enable surface mounting of the die to and interconnection with a printed circuit board (PCB). One conventional package configuration includes a leadframe having a die pad, and leads or lead terminals that mounts a semiconductor die top side up on the die pad. A die attach resin material (or paste) including a resin attaches the back side of the semiconductor die to the die pad which generally includes an epoxy-based resin, curing agent, catalyst, filler and one or more additives. Once the semiconductor die is attached to the die pad by the die attach resin, the assembly is usually cured, such as using ultraviolet light or oven curing, where the curing comprises crosslinking based on a material-specific thermal profile. The bond pads connected to active circuitry on the top side of the die are then wire bonded to the leads or lead terminals. After wire bonding, the die and leads or lead terminals are encapsulated in a mold compound such as a plastic material to form a semiconductor chip package generally leaving only the outer frame and the undersides of the leads or lead terminals exposed, with an option for an exposed die pad. After molding, the semiconductor chip packages are then cut from the outer frame (singulated).
One of the common issues encountered during semiconductor package assembly is referred to as resin bleed-out (RBO), or epoxy bleed-out (EBO), referred to herein as “resin bleed-out”. Resin bleed-out is the separation and movement of some of the components of the die attach resin material from the bulk material that is applied to the die pad. Depending on die attach resin material formulation and leadframe surface chemistry and morphology, resin bleed-out components can be solvents, reactive diluents, low-molecular-weight resins, catalysts, and additives such as an adhesion promoter. Resin bleed-out tends to occur on high energy surfaces that includes metal leadframe surfaces which lack an organic coating. Resin bleed-out can cause a variety of device problems, including the dielectric coating of the leads or lead terminals that prevents a proper connection to be made, and bond wire adhesion problems to the leads or lead terminals.
There are several known approaches for controlling resin bleed-out. These approaches include modifying the formulation by including an anti-bleeding agent, using a die attach film (DAF) or a B-stage epoxy material, controlling the leadframe surface roughness, creating a mechanical barrier, and lowering the surface energy of leadframes by a generally adding an organic surface coating.